Apparatus for raising or lowering a load



R. FORSTER.

APPARATUS FOR RAISING OR LOWERING A LOAD.

APPLICATION FILED SEPT. 4, 1920.

1,379,54 Patented May 24,1921.

Fig-4.

UNITE rice.

BUDOLF reissues,

$GHAF'J3, OF ESSEN-ON-THE-BUHR, GERMANY.

APPARATUS FOR RAISING OR LOWERING: A LOAD.

Specification of Letters Patent.

Patented May 24, 1921.

Application filed September 4, 1920. Serial No. 408,384.

T 0 all whom it may concern;

Be it known that I, Dr. RUDOLF Fiins'rnn, residing at Essen, Germany, a citizen of the German Republic, have invented a certain new and useful Improvement in Apparatus for Raising or Lowerin a Load, of which the following is a spe'cihcation.

This invention refers to an arrangement for raising or lowering a load by means of two simultaneously acting driving mechanisms, which are positively connected to the load and of which one only serves to 1111- part to the load the desired ascending or descending velocity, while the other s formed by an electro-motor which approximately compensates the weight of the load at all speeds. The object of the arrangement is to enable ascending or descending movements of any value and speed to be obtained independently of the weight of the load and without the aid of any starting. device, while the condition of movement of the first driving mechanism, which may be conveniently arranged to be worked by hand and which does not have to. perform any work of lifting but which has only to overcome frictional and inertia resistances, can

be adjusted in the most accurate manner to suit the speed which is to be imparted to the load and which varies with the working requirements.

The invention will he described with ref erence to the accompanying drawings in which Figure 1 shows a construction diagrammatically of an arrangement intended for winding up and letting down a hoisting rope according to the present invention, while trates the relationship whichexists between the most im :ortant electrical and mechani cal values 0 the arrangement.

. a hand crank a mounted on one end of the shaft, the other end ofwhich shaft a carries a spur wheel 9, with which gears a spur wheel a mounted on a countershaft C. A second spur Wheel a mounted on the shaft C gears with a spur wheel (i which is coupled to the shaft d? of the rotor D or an Fi 2 show" a vector dia rain which illusalternating current commutator motor D D The radio of transmission between the shafts 0. and d is such that the rotor shaft 03 rotates considerably more rapidly than the crank shaft a and such that a not too great speed of the crank a corresponds to the highest number of revolutions of the rotor shaft (Z occurring under like conditions.

The current is supplied to the rotor D of the motor D D by means of two brushes (Z (i running on the commutator d from an alternating current main F of constant tension and frequency. Between the main F and the rotor is placed the winding e of a choking coil E, the magnetic resistance of which can be regulated in the well known way (not shown) by varying the gap between the limbs e and e of its iron core. The exciting winding mounted on the rotor D of the motor D D is likewise connected to the alternating current main F across a regulating resistance G.

The choking coil E placed in the rotor circuit of the motor D D like the regulating resistance G placed in the exciting circuit is only for the purpose of stopping the turning moment developed by the motor D B, when at a standstill, and the magnitude of which under otherwise similar circumstances depends only, as is well known, on the tensions impressed on the stator and the rotor. By varying the gap between the limbs c and e of the choking coil E on the one hand and by adjustment of the resistance G on the other hand a means is afford- 90 ed of setting the turning moment of the motor D D in such a ratio with respect to the moment of the load acting on the shaft a of the drum, that the moment of the load is ust compensated.

After the load has been suspended from the hook I) and both the choking coil E and the resistance G so adjusted that the moment of the load is just compensated, the

' load can be raised or lowered by turning the ias only to perform such an amount for 1 5' 'thea ork,.tl1a(t inertia resistances of the load and the other parts moved are overcome and the losses by friction covered. The moment of the load is compensated when the motor is at a stand-still hy'its turning moment and 3.10

, In Fig. 2, H, 5 denote the vector of the tension of the mains, J K denoting the ohmic and K H t. inductive drop in the tension in the exciting circuit of the motor D D. The field J N of the motor, value of which is a. function f the strength of the exciting current on A it invariable also oscillates in phase with the vector of the ohmic drop in the tens h with the exciting -'Clllit" 31t.

duced in it, which is to its number of rovolda'oior likewise the same phase rent. According es the d cacti. n or no tion of the rotor, the vector oi? [the conn electromotive force is of simil; direction with the vector of i eld of opposite direction thereto. Thus, for the vector J M denotes, eccordi: to its Inegnitude and. direction, CC'llilLJ@1"-1%CirGHO- tive force which is set up when lo'ed is raised cut a. certain speed, and J the coon; ter-electromotive force which ex ts during the lowering of the load.

In one case ther fore M and other H H must indice'il. he vector total drop in the tension in the cuit. 'T his drop in the tension M can be again divided into the ohmic drop M P or R S and the inductive drop S H, when it is considcned thet the ratio of the ohmic resistance to the inductive rcsis/canoe, and therefore ale-o JlO of the corresponding drops in the ion and accordingiy the tangent of the angle opposite the vector M P or R S always remains equel to itself.

Instead of projecting ohmic drop in the tension in the cuit M P or R S on to the field vector J N, We may, for the of greater cleernes's (as-has been done in Fi 2 the of the project the vector of the inductive disc in the rotor circuit on to the vector of the inductive crop in the exciting circuit (H K}, which. is at right anglesto the fieid vector, in order thereby to obtain a, measurement for the turning moment developed by the motor. The section'H Q accordingly corresponds to the turning moment developed when the load is ncised the assumed descending velocity when the load is lowered. The section H l; repi'esenin, measured on the some scale es H Q and H T, with great approximation the turning moment which is e'fl'ectivo when the motor is at a standstill and just compensates the iced. It follows at once from a. comparison of the three sections H Q,H K and H T, that all three turning moments are of almost the same magnitude. The divergences, which es itis smell, will of course bestill less for speeds which lie between those assumed.

Furthermore it is obviously possibie,.

Without its being neces my to edduce any proof in support thereof, by reducing the ohmic ceslstence in the exclting circuit rela- -tively to the corresponding inductive resis once, to still further reduce the aforesaid divei'gencee if necessary. course instead of xthe hand crank a any other driving mechanism, such as e motor driven one for example, might be used Without departing from the spirit of the invention. the hand operated driving mechanism however pro 'ides the edwantage that the ascending or descending movements of the load can be eflcoted with a fine degree of pen-ception which cannot be secured, Whennsing any motor opera-ted arrangement.-

Clcinis. I

1. In a. hoisting mechanism, the combinetion of means for impeding the desired ascending end descending velocity, and means comprising an elective-motor for eppronimetely compensating for the load at any speed.

2. Apparatus such as set forth in claim 1, in which the coinpenseting. motor is e. shunt wound commutator motor, having" an alternating cui'i'en t source of constnnt tension and frequency and the rotor circuit of which has, in comparison with its ohmic resistance, a high inductive resistance.

8, Apparatus such es set forth in claim 2 in which the rotor has in circuit a, choke coil having reguleteble magnetic resistance.

4. Apparatus such as set forth in claim 1, having hand driven moons for imparting the desired. velocity to the load.

The fonegoing specification signed at Essen, Germany, this 12th day of June, 1920.

D12. RUDOLF FQBSTER.

in presence oi? HANs GoTTsMANN, Josnc Oneness. 

